1. Field of the Invention
The present invention relates in general to a method of fabricating a liquid crystal display (LCD). In particular, the present invention relates to a method of fabricating an alignment-control structure and a reflective layer of an LCD.
2. Description of the Related Art
Applied voltage and heat on a liquid crystal display (LCD) changes the alignment of liquid crystals from an initial specific status to another status, and then the accompanied optical characteristics, such as double refraction, optical rotation, dichromatism, optical confusion and optical scattering will be transformed into visional variation. Compared with the electric-optical materials used in other optical devices, the liquid crystals can distribute substantial variation in optical characteristics with low voltage and low electric power consumption and without further working and shaping treatment. Also, LCD has advantages of thin shape and light weight. Therefore, LCD plays an important role on the flat display market.
The display mode of LCD is different from the type of the liquid crystals thereof. One mode named electrically controlled birefringence (ECB) employs applied electric field to control the multi-refraction characteristics of the liquid crystal, wherein nematic crystal having a negative anisotropy of its dielectric constant is utilized together with a vertical alignment layer. When the applied voltage exceeds the critical voltage, the liquid crystal molecules that are originally aligned perpendicular to the vertical alignment layer will rotate at an angle corresponding to the applied electric field. Besides, for further controlling the alignment of the liquid crystal molecules, an alignment-control structure is fabricated on the LCD substrate to increase the amount of alignment domain in a pixel area. This is possible to secure a wide visual field angle and a high contrast.
Please refer to FIG. 1. FIG. 1 is a cross-sectional schematic diagram of an LCD cell 10 according to the prior art. The LCD cell 10 comprises an upper glass substrate 12, a lower glass substrate 14, and a liquid crystal 16 with a negative anisotropy of its dielectric constant filling the space between the two glass substrates 12, 14. Two electrodes 18, 22 and two vertical alignment layers 20, 24 are respectively formed on the inner surface of the glass substrates 12, 14, and two polarizers 26, 28 are respectively formed on the outer surface of the glass substrates 12, 14. In general, the upper glass substrate 12 serves as a color filter substrate. The lower glass substrate 14 serves as a thin film transistor (TFT) substrate where a plurality of TFTs and active matrix drive circuits are formed and the electrode 22 on the lower glass substrate 14 serves as a pixel electrode. Furthermore, the LCD cell 10 comprises a plurality of first protrusions 30 and second protrusions 32 respectively formed on the electrodes 18, 22 to serve as the alignment-control structure.
Please refer to FIG. 2. FIG. 2 shows the variation in alignment of the liquid crystal molecules. In the case where the liquid crystal 16 having a negative anisotropy of dielectric constant is arranged between the vertical alignment layers 20, 24, all the liquid crystal molecules are aligned in the direction perpendicular to the vertical alignment layers 20, 24 when no voltage is applied thereto. The liquid crystal molecules 16A are aligned in the direction perpendicular to the glass substrates 12, 14. The liquid crystal molecules 16B, 16C positioned on the slopes of the protrusions 30, 32 are aligned at an angle to the vertical alignment layers 20, 24. Upon application of the voltage to the LCD cell 10, the crystal liquid 16 rotates toward the electric field wherein the alignment variation is shown by the arrows. As a result, part of the liquid crystal molecules rotate in the clockwise direction and another part of liquid crystal molecules rotate in the counterclockwise direction to accordingly increase the amount of alignment domain in a pixel area.
Please refer to FIG. 3A to FIG. 3C. FIG. 3A to FIG. 3C are schematic diagrams of a method of forming the alignment-control structure according to the prior art. First, a polymer resin layer 38 possessing photosensitive and thermosetting characteristics is coated on an electrode 36 of a glass substrate 34, and then a curing treatment is performed on the polymer resin layer 38. Next, by using a photoresist layer with strip-shaped openings (not shown), the exposure process and the photolithography process are performed to form the polymer resin layer 38 as a plurality of strip-shaped protrusions 39. Finally, a heat treatment is applied to make the polymer resin layer 38 reflow, and thereby the sharp-pointed edge of the protrusion 39 is rounded to complete the preferred alignment-control structure.
However, the planar area on the top of the protrusion 39 with a round profile is too large. The liquid crystal molecules positioned thereon (such as the liquid crystal molecules 16C shown in FIG. 2) is affected by a weaker electric field, and therefore sways toward the left and right since the aligned direction is not determined. This may result in spots or dark lines on the display screen and affect the display quality. In order to solve the problem, the alignment-control structure is designed as an approximate triangle profile to decrease the planar area on the top of the protrusion as much as possible. Unfortunately, this preferred protrusion is made of stacked layers by repeating deposition, photolithography and etching processes those complicated processes increase not only process cost but also difficulty in process property.
An object of the present invention is to provide a method of fabricating an alignment-control structure having a triangle profile to solve the above-mentioned problems.
The present invention provides a method of fabricating a liquid crystal display (LCD). First, an organic layer is formed on a glass substrate and then a pattern layer is formed on the organic layer. Next, by employing an attenuated mask, the pattern layer is formed as a plurality of first protrusions that are unconnected with each other and each of the first protrusions has a ladder profile. Next, a dry etching process is performed to remove all of the first protrusions and part of the organic layer so as to form the remaining organic layer as a plurality of second protrusions corresponding to the first protrusions. The second protrusion has two sloped and intersected sidewalls.
This and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings.